The Optical Rain Gauge (ORG) uses an infrared laser beam to measure total rain accumulation and rain rates. The instruments functions similar to a the laser beam at the base of a garage door to detect objects (ie. children) in the path of the closing door. The instrument functions by emitting a continuous laser beam at a detector. As long as nothing crosses the path of the beam, the instrument reports no rain. When a rain drop (or anything) falls through the path, the laser is obstructed and the detector sees less intensity (scintillation). The amount of laser obstructed is then used to calculate the rain drop cross section and a volume of water can be estimated by assuming a spherical or semi-spherical volume of liquid. In theory this method could be more accurate at detecting all rain drop sizes and capable of measuring very small amounts of precipitation. Although, the process is susceptible to bugs, dirt, leaves, ... The ORG will typically report more precipitation than a Tipping Bucket Rain Gauge (TBRG), but the two should agree well when the intensity and or total accumulation is significant.